Based on the propagation law of partially coherent light, the spectral changes of Gaussian Schell-model (GSM) beams passing through an astigmatic aperture lens are studied. It is shown that as compared with the original spectrum of the source, the axial spectrum in the focused field shifts to lower or higher frequency, which is defined as a spectral shift. Thedependence of spectral shift of GSM beams on the astigmatism of the lens, spatial coherence of GSM beams and the aperture diffraction is investigated in detail. The numerical results show that these parameters affect the spectral shift noticeably. A comparison with the aberration-free case is made, and shows that the astigmatism affects the spectral behavior of GSM beams, the largerastigmatism results in larger spectral changes in general.